Standardised on "apphook" throughout docs

Existing examples included: AppHook, App-Hook, Apphook, apphook, app-hook

"Apphook" has been chosen for pragmatic reasons (for example, it reflects naming in the code
itself), and we must simply live with the stain of its ugliness on our consciences until we have
expunged it through penance and good deeds.

Also added a note on the future use of spaces rather than tabs in frontend ccode.